Children with specific language impairment often show an especially serious limitation in the use of grammatical morphology. These difficulties include problems with bound morphemes such as past tense and third person singular inflections, and function words such as articles and auxiliary verbs. The purpose of this project is to explore the possible bases of these grammatical morpheme limitations, and to examine how such limitations may hinder other aspects of these children's language development. To accomplish this general goal, specifically language-impaired (SLI) children's comprehension and production of grammatical morphemes will be examined across four different languages: English, Hebrew, Italian, and Swedish. Data from these different languages will be used to assess the relative adequacy of three recent accounts of English-speaking SLI children's problems with morphology. Because the morphological properties of these languages differ from those of English in critical ways, they offer a clearer view of the contribution of factors that are confounded in English, thereby facilitating interpretation of the data obtained from the English-speaking SLI children. Inclusion of these other languages will also permit a stronger test of whether problems in word order are related to deficits in morphology. An understanding of the source of SLI children's problems with morphology and the role these problems play in other areas of language should lead to more appropriate treatment procedures for these children.